Hand held power tools are well known. Typical power drills and power screw guns have a handle which extends downwardly and from the rear of a drive motor. The drive motor rotates about an axis substantially perpendicular to the handle and with the front end of the drive motor being coupled as to a chuck for holding drills or to a screw bit which rotates parallel the axis of the drive motor. Such power tools have the disadvantage that the weight of the motor is forward of the handle and must be supported by the strength of a user's hand manually holding the tool.
Screwdriving apparatus are known for collated screws. Typical apparatus of this type are illustrated, for example, in U.S. Pat. No. 3,930,297 to Potucek et al, issued Jan. 6, 1976, U.S. Pat. No. 5,027,679 to Kawashima et al, issued Jul. 2, 1991 and U.S. Pat. No. 5,186,085 to Monacelli, issued Feb. 16, 1993. Each of these patents show a power screw gun having a handle rearward of the motor and extending downwardly therefrom and an attachment coupled to the front of the screw gun which is adapted to feed collated screws in a manner that successive screws may be driven on the tool being successively urged forwardly into a workpiece. A preferred attachment for such devices is shown in U.S. Pat. No. 4,146,071 to Mueller et al, issued Mar. 27, 1979.
A disadvantage of power tools generally with a handle rearward of the motor and particularly of such devices when used for driving collated screws is that the handle is distanced from the workpiece to be engaged which causes difficulty in control as well as increased weight to be supported by the hand of a user.
U.S. Pat. No. 4,623,597 to Cast issued Dec. 2, 1986 and U.S. Pat. No. 5,109,738 to Farian et al, issued May 5, 1992, teach collated screwdriving apparatus in which a handle extends perpendicularly from the axis of a motor and is located under the motor, that is, forwardly from the rear of the motor. These devices while, to some extent, overcome the difficulties of having the substantial weight of the tool forward of the handle, continue to have the disadvantage of resulting in a large tool and with the substantial weight of the motor supported above the handle and in the way of a user of the tool.
Another disadvantage of known hand held power tools, such as typical power drills and screw guns, is that a trigger switch is provided on a forward end of the handle which trigger switch must be drawn towards the handle by the fingers of a user in order to operate the tool. This has the disadvantage of being tiring to a user when a tool is used for an extended period of time. Some tools are provided with a locking mechanism which permits the trigger to be locked in an operative position, however, this has the disadvantage of being unsafe in certain circumstances.